Titanium alloy beryllium composites



United States Patent TITANIUM ALLOY BERYLLIUM COMPOSITES StanleyAbkowitz and Warren L. Larson, Lexington, and

Fortunate J. Rizzitano, Needham, Mass.; said Abkowitz and said Larsonassignors, by direct and mesne assignments, of two-thirds to WhittakerCorporation, Los

Angeles, Calif., a corporation of California No Drawing. Filed May 13,1966, Ser. No. 549,781

Int. Cl. B22f 7/02 US. Cl. 29-492 2 Claims ABSTRACT OF THE DISCLOSUREThe invention relates to composites of titanium base alloys andberyllium, and more particularly to titanium alloy beryllium compositesin which the titanium alloy component of the composite, for example, mayprovide very high yield and tensile properties in combination with goodductility, and in which the beryllium component of the compositeimproves the modulus of elasticity and the strength-to-density ratio,while the ductile matrix of the titanium phase is maintained.

Titanium products having presently nnobtainable combinations ofproperties continue to be in demand, particularly in the construction ofaircraft such, for example, as supersonic transport planes.

For certain applications, known commercial titanium alloys have not beenavailable which combine the properties or characteristics of very highyield and tensile properties, good ductility, a favorable modulus ofelasticity, and a high strength-to-density ratio. Such material isneeded particularly where high temperature strength has been required.For lower temperature applications toughness and ductility combined withan improved modulus of elasticity and strength-to-density ratio are adesired combination of properties not available in commercial titaniumalloys.

Accordingly, objectives of the invention are to satisfy the existingneed; to provide new high temperature strength titanium alloy berylliumcomposites which have an improved strength-to-density ratio and animproved modulus to density ratio, along with very high yield strengthand tensile properties and good ductility; to provide new titanium alloyberyllium composites for lower temperature applications which combinetoughness, ductility and improved modulus of elasticity andstrength-to-density ratio; to provide new procedures for the manufactureof such composites whereby the stated extraordinary combination ofproperties may be obtained; and to achieve the stated objects simply andeitectively thereby solving existing problems.

ice

These and other objects and advantages may be obtained, the statedresults achieved and the described difficulties overcome by theconcepts, discoveries, principles, procedures, methods, steps,treatments, compositions, composites, products and combined propertieswhich comprise the present invention, the nature of which is set forthin the following general statements, preferred embodiments ofwhich-illustrative of the best modes in which applicants havecontemplated applying the principles-are set forth in the followingdescription, and which are particularly and distinctly pointed out andset forth in the appended claims.

The nature of the concepts and discoveries of the invention relating tohigh temperature strength composites of a. titanium alloy and berylliummay be stated in general terms as comprising a ductile composite millproduct having room temperature properties of about 7.5% elongation, 17%reduction of area, and 188,000 p.s.i. yield strength, formed of atitanium base alloy (Ti-6Al-4V) and beryllium, the titanium alloy andberyllium components of the composite being formed as microquenchedage-formed shot, the components being blended in the proportions byvolume of 90% titanium 'base allo and 10% beryllium, and the blendedcomponents being hot compacted and extruded at 1300" F. to form thecomposite mill product.

The nature of the concepts and discoveries of the present inventionrelating to titanium alloy beryllium composites for lower temperatureapplications comprise a mill product consisting of from 20% to berylliumand the balance a titanium alloy formed as a composite frommicroquenched age-formed beryllium and titanium alloy componentmaterials blended, compacted and extruded at 1300 F.

The nature of the concepts and discoveries of the invention relating tothe manufacture of the improved composites may be stated in generalterms as including the steps of providing titanium alloy and berylliumcomponent materials for a composite to be formed in microquenchedage-formed particle state; blending the particles in the desiredproportions; consolidating and extruding the blended particles at atemperature not in excess of 1300 F. to bond the component particlestogether; and controlling the temperature of the components duringcompacting, bonding and extrusion to below that temperature at whichharmful diffusion of the components with one another can occur.

In accordance with the invention, a desired titanium base alloy havingusual typical mechanical properties as to strength and ductility isconverted to high purity powder form to produce microquenched age-formedparticles of the alloy in the manner set forth in Kauffman Pat. No.3,099,041. The conversion of the selected titanium alloy material tomicroquenched, age-formed particles substantially improves themechanical properties of the alloy as compared with the typicalproperties of the alloy, such that very high yield and tensileproperties in combination with good ductility are provided.

Also, in accordance with the invention beryllium similarly is convertedin the manner set forth in Pat. No. 3,099,041 into beryllium shot, thatis microquenched, age-formed particles of beryllium. Beryllium has ahigh modulus of elasticity and a lower density than titanium and itsalloys. Thus, the formation of a composite of a selected titanium alloyand beryllium will improve the modulus of elasticity and thestrength-to-density ratio of the composite as compared to theseproperties of the titanium alloy component while maintaining the ductilematrix of the titanium phase in accordance with the concepts of theinvention.

The titanium alloy and beryllium in shot form then are blended in thedesired proportions to obtain the desired combination of properties. Theblend of shot then is heated, compacted, consolidated, bonded andextruded by plastic deformation reduction and working to the necessaryextent or degree to form the desired mill product.

In accordance with the invention and illustrative of the new concepts, atitanium alloy having desired properties is employed as a component ofthe composite to be formed. For example, the Ti6Al-4V alloy typicallyhas a tensile strength of 150,000 p.s.i. with 19% elongation. We havediscovered that the Ti-6A1-4V alloy when converted into microquenchedage-formed particles or shot and the sho compacted and extruded undercontrolled temperature conditions, in accordance with the procedures setforth in the Abkowitz copending application Ser. No. 335,799 (now patentnumber 3,343,998, dated Sept. 26, 1967) and in the Abkowitz et al.copending application Ser. No. 447,119 (now Patent No. 3,368,881, datedFeb. 13, 1968), it develops a tensile strength of 202,000 p.s.i. with14% elongation. However, such alloy material for certain applicationsalso should desirably have a higher strength-to-density ratio and a morefavorable modulus of elasticity.

Beryllium has these desired properties of low density and a highmodulus. However, when beryllium is introduced into a titanium alloy asan alloying element or by interdifiusion, brittle intermetalliccompounds are produced which are detrimental to mechanical properties ofthe alloy.

However, we have discovered that if beryllium also is converted tomicroquenched, age-formed, shot, it may be blended, compacted, bondedand extruded with similar titaniumalloy shot to form a composite which,when the temperature is critically controlled at about 1300 F. duringcompacting and extrusion of the composite material, retains to a highdegree the favorable properties of both components of the composite.

Various titanium alloy beryllium composites of the invention weremanufactured in accordance with the procedures described below. Afterthe titanium alloy and beryllium separately were converted tomicroquenched age-formed particles or shot, the shot was Weighed andappropriate amounts of each component were mixed or blended to obtain asuniform a mixture as possible. The blended mixture was then introducedinto cans or containers preferably formed of seamless low carbon steeltubing with welded-in end plates. As the cans or containers were filledwith the blend, the shot in the cans was cold compacted with anhydraulic press prior to welding the top end plate for the can.

The steel end plate at the top of each can of cold compacted shot blendthen was welded closed, and during welding a flow of argon was directedthrough an evacuation tube connected with the interior of the can toprevent oxidation of the shot from heating. The can of cold compactedshot then was evacuated to a final pressure of less than 0.5 micronwhile being heated at 800 F. After three hours of such hot outgassing,the can was cooled to room temperature after which the evacuation tubewas hot forge-sealed.

Hot compacting of the material in the cans-then was carried out in aliner of an extrusion press using penetrating tools heated to about 900F. placed at both the front and rear of the can containing the shotmaterial. During application of a 600-ton load, the press ram forced thepenetrators against the end plates into the inside of the teel can aftershearin the W tl e ween e en plates and the can. The billets or cans topermit hot-cornpacting were heated to the same temperature subsequentlyused as an extrusion temperature for the material as described below.

The hot compacted cartridge thus formed after proper machining toaccommodate subsequent extrusion operations then was repeatedly extrudedWhile jacketed or canned through a number of reductions to form extrudedrods in the manner described in detail in said Abkowitz application Ser.No. 335,799 (patent number 3,343,998). Various hot compacted blendproportions of composite components in preparation for extrusion wereheated to extrusion temeratures of 1100 F., 1300 F., and 1600 F. forcomparable evaluation of the extruded composite products. Heattreatments of the extruded rods were carried out prior to the removal ofthe steel canning material. For rods extruded at 1100- F. and 1300 F.,the heat treatment comprised aging at 1050 F. for three hours and thenair cooling. The rods extruded at 1600" F. were solution heat treatedfor fifteen minutes at 1600 F. followed by a water quench and then agingat 1300 F. for three hours and then air cooling. Other rods extruded at1600 F. were annealed at 1300 F. for three hours and then air cooled.Test specimens were machined from heat treated rods for evaluation ofmechanical properties. The mechanical test properties of the compositesare summarized in Table I on the following page.

Metallographic examination of the 10 v/o beryllium composites extrudedat 1100 F. (both primary and secondary extrusions) indicated smoothinterfaces between the beryllium and titanium phases, with no evidenceof voids or compound formation. Similar composites extruded at 1600 F.revealed considerable amounts of intermetallic compound between theberyllium particles and the titanium alloy matrix, and also manyassociated void areas. The 20 v/o beryllium composite, extruded at 1600F., had many more void areas in the structure because of the greaternumber of beryllium particles. The presence of considerable amounts ofboth brittle intermetallic compound and void areas in the structureaccount for the lowered strengths and ductilities obtained in the 1600F. extruded composites, with the 20 v/o beryllium samples showing lowerproperties than those with 10 v/o beryllium.

The composites with 10 v/o beryllium extruded at 1100 F. provided highstrength but low ductilities resulted rendering such materialunsatisfactory. Similar 10 We beryllium composites extruded at 1600" F.involved excessive interaction between the beryllium and titanium phaseswhich resulted in lower mechanical properties with essentially noductility.

Subsequent metallographic investigation of samples of the 10 v/oberyllium composite heat treated at 1200 F., 1300 F., 1400 F. and 1500F. for three hours disclosed that there was no intermetallic reaction at1200 F. or 1300 F. However, at 1400 F. some compound formation wasevident and at 1500 F. considerable compound was formed, as well as theusual void areas.

These discoveries led to further evaluation of billets extruded at 1300F. formed of composites of 10 v/o and 75 v/o beryllium, and also one ofv/o beryllium or all beryllium. The mechanical test properties of thesecomposites extruded at 1300 F. also are listed in Table I. The 1300 F.extrusion temperature used for these composite products is Within theaging temperature range that must not be exceeded in heat treatingmicroquenched ageformed materials in order that the obtained combinationof strength and ductility achieved through microquenching andage-forming is not lost.

The mechanical properties of the 10 v/o beryllium composite extruded at1300 F. are a distinct improvement over those obtained with the 1100 F.or 1600 F. processing temperatures. An excellent combination of tensilestrength, ductility, and impact properties is indicated. Thus, referringto samples, the L-samples in Table I, the material Comparing theproperties of the Ti-6Al-4V alloy and the 10 v/o beryllium compositedata in Table I, the B- samples represent about the highest strengthsand ductility that can be obtained for the Ti-6Al-4V alloy even usingmicroquenched material which is not age-formed, since the extrusiontemperature of 1600 F. is above the age-forming temperature range; andit is only by forming below age-forming temperature that maximumstrength is obtained.

Similarly, the C-samples in Table I illustrate that a different heattreatment reduces strength somewhat from the B-samples but givesincrease ductility for the Ti-6Al-4V alloy. The D-samples illustrateexcellent mechanical properties obtained by processing the Ti-6Al-4Vmaterial by "microqu'nching and age-forming. Tensile strength of above200,000 p.s.i. and ductilities as high as 14% elongation were obtained.

Referring to the E-samples, with the addition of 10% beryllium in acomposite extruded at 1100 F. in an attempt to impart the favorableproperties of beryllium to the composite resulted in low ductilities.

Increasing the extrusion temperature for the 10 W beryllium composite to1600 F. with different heat treatments (H-samples and J-samples)resulted in reduced strengths with essentially no ductility.

The L-samples show that using the critical extrusion temperature of1300" F., the We beryllium composite retains the high tensile strengthof the D-samples with substantial ductility, and with improvedstrength-todensity and modulus-to-density ratios as well as favorableimpact properties. Thus, the 10 We beryllium composite provides anextraordinary combination of tensile strength, ductility, improvedimpact properties and improved strength-to-density andmodulus-to-density ratios.

Thus, in accordance with the invention using the 13 00 F. extrusiontemperature, the microquenched shot of the blend is easily consolidatedand bonded with minimum diffusion, and at the same time age-forming ispossible to retain the benefits of microquenched, age-formed material bywhich high strength with ductility is obtained. To these advantages isthe added further advantage of the ability to add beryllium to the highstrength material to impart the favorable properties of beryllium to thecomposite.

Strength properties of the improved titanium alloy beryllium compositesmay be predicted reliably in accordance with the arithmetic proportionof the component from which the property is derived that is present inthe composite.

For example, conventionally heat treated commercial Ti-6Al-4V alloy hasan average yield strength of about 150,000 p.s.i. Beryllium has anaverage yield strength of about 75,000 p.s.i. It is possible tocalculate the yield strength of the 10 v/o beryllium composite by adding90% of 150,000 or 135,000 to 10% of 75,000 or 7,500 which equals 142,500which approximates the yield strength of the G-samples of a compositeformed without age-forming.

Similarly, adding 90% of 200,000 (the approximate yield strength of theD-samples) or 180,000, to 10% of 75,000 or 7,500 equals 187,500 p.s.i.yield strength for the 10 v/ 0 beryllium composite formed frommicroquenched age-formed material. This is substantially exactly thestrength value of the L-samples.

Referring to the 75 We beryllium composite and the 100 v/o berylliummaterial (R-samples and O-samples of Table I), extruded at 1300 F.,while low tensile strengths and ductility are present, there is improvedimpact strength for the 75 We beryllium composite as compared with the100 v/o beryllium, as well as high modulus values.

It is evident from comparison of the similarity of the H and Lsamplesextruded at 1600 F. of 10 v/o and 20 v/o beryllium composites with the10 v/o beryllium composite L-samples extruded at 1300 F., thatcomposites of from 20 v/o to 75 v/o beryllium will have improvedductility when extruded at 1300 F.

Although the invention has been described with reference to compositesformed of beryllium and the Ti6Al-4V alloy, it is understood thatcomposites of beryllium and other titanium alloys or unalloyed titaniumprocessed in accordance with the invention with microquenched age-formedmaterial extruded at 1300 F. will exhibit improved properties ascompared with the commercial titanium alloys themselves.

Accordingly, the invention provides new titanium alloy berylliumcomposites having extraordinary combinations of properties which satisfyexisting needs and solve problems in the art, and provides newprocedures for the manufacture of such composites'in a simple"and'eifective' manner.

In the foregoing description certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchterms are used to descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention and the newprocedures and products are by way of example and the scope of theinvention is not limited to the exact details described, because variousproducts may be manufactured without departing from the fundamentalconcepts and principles of the invention.

Having now described the features, concepts, discoveries and principlesof the invention, the characteristics and properties of the newproducts, the preferred procedures to be used, and the advantageous, newand useful results obtained; the new concepts, discoveries, principles,procedures, methods, steps, treatments, compositions, composites,products and combined properties, and mechanical equivalents obvious tothose skilled in the art are set forth in the appended claims.

We claim:

1. A ductile composite mill product consisting essentially of a mixtureof microquenched, age-formed shot particles of Ti-6Al-4V alloy andmicroquenched, ageformed shot particles of beryllium in the proportionby volume of 10% beryllium and the balance Ti6Al4V alloy, said particlesbeing bonded together free of intermetallic compound formation betweenthe Ti-6Al-4V alloy and beryllium particles by hot compaction andextrusion of the mixed particles at 1300 F. such that the extruded millproduct has room temperature properties of from 6.3 to 7.5% elongation,11.2 to 18.9% reduction of area and 176,500 to 188,500 p.s.i. yieldstrength.

2. A composite mill product consisting essentially of a mixture ofmicroquenched, age-formed shot particles of Ti-6Al-4V alloy andmicroquenched, age-formed shot particles of beryllium in the proportionby volume of from 10% to 75% beryllium and the balance Ti-6A1-4V alloy,said particles being bonded toegther free of intermetallic compoundformation between the Ti-6A1-4V alloy and beryllium particles by hotcompaction and extrusion of the mixed particles at 1300 F.

References Cited UNITED STATES PATENTS 2,754,204 7/1956 Jafiee 75175.5

3,099,041 7/ 1963 Kaufmann 264-8 3,196,007 7/ 1965 Wikle 29182 X3,325,257 6/1967 Ang 75-l50 CARL D. QUARFORTH, Primary Examiner A. J.STEINER, Assistant Examiner US. Cl. X.R.

